Resin is like cement in reinforced concrete,
or muscle in the human body.Fibers are like concrete and steel, like bones in
the human body.Resin is the matrix and fiber is the skeleton.Each plays an
independent role in FRP, but it is not isolated, but caused by shear
deformation.

Strength of FRP to the glass fiber, both
strength and modulus of elasticity, much worse than fiberglass resin, however,
FRP bending, interlaminar shear and compression parallel degree, to a large
extent depends on the resin again, for the tensile strength, although depending
on the glass fiber, but still can't ignore the effect of resin.As for the role
of resin, there are three aspects:

1. Adhesion: different resins have different
adhesion forces. For example, epoxy resins have various polar groups,
especially the possibility of a chemical bond between epoxy and glass, which is
the advantage of epoxy.The advantages of polyester resin infiltration are good,
and there are more interconnection points.However, phenolic resin makes up for
its deficiency with the advantage of high crosslinking density.In FRP, the fibers
do not want to touch each other, and it is best to be dispersed in order to
function as a skeleton.Fiber and resin bond in one direction FRP, when the
direction of force is perpendicular to the direction of fiber, the strength is
not related to the fiber content, but to the resin itself and resin and fiber
bond.

2. The function of load transfer and balanced
load: glass fiber has high tensile capacity, but a bundle of fiber cannot be a
component, and can only be used as a component after FRP is made.The resin
transfers the load to the fiber, so the upper fiber is compressed, the lower
fiber is pulled, and the middle part is cut.The shear stress is borne by the
resin.Of course the interlaminar shear strength of FRP is low, about 1/10 of
the tensile strength, resin load is not only to play the role of a balanced
load, such as the presence of a few bearing is not the function of fiber, resin
will maximize give it, the load transfer equilibrium distribution to all who
hold fiber.However, because the fiber can cause various defects in the
production process, the fiber has never actually reached its theoretical
strength.

3. The function of the resin itself:
different types of resin have different effects, which requires selective use,
such as higher strength of epoxy than polyester and phenolic.Same polyester,
different properties, rigid, flexible no. 195 transmission, DAP transmission,
no. 197 corrosion resistance.In glass fiber, there is no alkali ratio in high
strength and heat resistance.High strength fiber is stronger than non - alkali
fiber.